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New research suggests that, for people with clogged arteries in the legs, even the simple act of walking may depend on having hefty calves.

The study, published in the January 31, 2011, issue of the Journal of the American College of Cardiology, focused on mostly elderly men and women with peripheral arterial disease (PAD). It found that, as the disease worsened over time, women were far more likely than men to lose the ability walk more than a few feet at a time.

PAD is akin to heart disease of the legs. A build-up of cholesterol narrows the arteries and restricts blood flow to the leg muscles. Typically, one of the first symptoms is pain, cramping or fatigue in the legs while walking that goes away with rest.

For the study, 380 patients with PAD participated in several tests aimed at measuring the effect of PAD on their ability to walk. The tests were repeated each year to document any changes. Among the tests were the:

Six-minute walk test, which involves walking up and down a 100-foot hallway for 6 minutes in an attempt to cover as much distance as possible;

Four-meter walking velocity test, in which patients walk 4 meters (about 13 feet) at a usual pace and again at their fastest pace; and

Mobility questionnaire, which asks patients whether they are able to walk a quarter mile or up and down a flight of stairs without assistance.

Patients also had CT scans of their lower legs to measure the size of the calf muscle and tests to measure knee strength.

Over four years of follow-up, the researchers found that women were far more likely than men to experience a decline in the ability to walk and in overall mobility. For example, women were more than twice as likely to lose the ability to walk continuously for 6 minutes without stopping, and nearly twice as likely to report that they could no longer walk a quarter mile or climb a flight of stairs. They also experienced a significantly greater decline in how far they could walk in 6 minutes and in how fast they could walk at their usual pace.

However, when researchers looked more carefully at the data and accounted for the fact that men had bulkier calf muscles to start with, differences between women and men in function and mobility disappeared.

Researchers speculated that although PAD causes a shortfall in blood flow and oxygen to the calf muscles of both men and women, men have extra muscle to draw on, and this gives them enough remaining strength to continue walking. Women, on the other hand, may already be using all of their available muscle to walk by the time PAD is diagnosed, so the long-term effects of the disease are more devastating.

More studies are needed to determine whether helping women to build up their calf muscles once they are diagnosed with PAD will also help them retain the ability to walk.

Questions for You to Consider

How is PAD diagnosed?

Doctors often diagnose PAD by using the ankle-brachial index (ABI) to assess blood flow to the legs. The ABI is a simple test that can be done in your doctor’s office. During the test, you lie flat while your doctor measures the blood pressure in both arms using a standard blood pressure cuff and a small hand-held Doppler ultrasound probe. The ultrasound probe detects the first sound of blood flow as the cuff is deflated; that’s the upper number in your blood pressure. Your doctor then measures the blood pressure in both ankles by placing an inflatable blood pressure cuff between the ankle and calf and again using the Doppler ultrasound probe to listen for blood flow.

The next step is to calculate the ratio of the highest ankle pressure to the highest arm pressure on the same side of the body. This is the ankle-brachial index. If the blood pressure in the ankle is a lot lower than in the arm, it is a sign that a blockage is interfering with blood flow to the lower leg.

If I’m diagnosed with PAD, what can I do to keep it from getting worse?

The best way to prevent PAD from getting worse is to practice good health habits and take the medication your doctor prescribes. Some of the healthy steps you can take include:

Stop smoking. The toxins in cigarette smoke damage the lining of your blood vessels, while the nicotine constricts your arteries, further cutting off blood flow to your legs. Stopping smoking is the single most important lifestyle change you can make in preventing PAD from getting worse.

Get more exercise. It may seem surprising that someone who is having pain while walking should start a regular exercise program that includes more walking, but it’s true. As you gradually build up your walking distance and speed, you will develop new blood vessels, build up your calf muscles, and train your muscles to use oxygen more efficiently.

Eat a healthy diet. PAD is like heart disease in the legs, so you should follow a heart-healthy diet. Eating lots of fruits, vegetables and whole grains, while limiting your intake of high-fat meats and processed foods will help you achieve a low-fat, low-cholesterol, low-salt diet.

Take your medications. Your doctor may prescribe medications to lower your cholesterol level and keep your blood pressure in check. In addition, dangerous blood clots are more likely to form in arteries clogged with cholesterol deposits. Your doctor may prescribe aspirin, Plavix or another medication to reduce the risk of blood clots.